Methods for performing sterilization by producing hypochlorite from salt water have already been proposed. For example, a method for producing hypochlorite by electrolysis using a cation exchange membrane has been proposed (Patent Document 1).
When sterilization is performed using hypochlorite, it is sometimes preferable to remove the residual hypochlorite after the sterilization. As a result, methods for removing hypochlorite have been proposed. For example, a method has been proposed in which a water for treatment containing an available chlorine component is supplied to a single-electrode electrolytic cell, and the available chlorine component is decomposed or reduced at the cathode (Patent Document 2). Patent Document 2 discloses the use of a carbon-based material as the cathode material, and discloses that the application of a low voltage which is accompanied by substantially no gas generation is preferable.
Further, a method in which the production and decomposition of hypochlorite are achieved by application of a voltage has also been proposed (Patent Document 3). Patent Document 3 discloses that by using a pair of AC electrodes and two prescribed ground electrodes, the generation and reduction of sodium hypochlorite is possible.
The method of Patent Document 1 requires the use of a cation exchange membrane, and therefore regeneration of the cation exchange membrane is necessary, control of the apparatus is complex, and the maintenance costs tend to increase. Further, Patent Document 2 discloses only a method for reducing the concentration of free chlorine. Furthermore, Patent Document 3 includes no indication of the size of the effect actually achieved using the method of Patent Document 3, and therefore the effectiveness of the method of Patent Document 3 is unclear.